Field of the Invention
The field of the inventive embodiments disclosed here relates generally to systems and methods for electromechanical or electromotive drives, and more particularly the inventive embodiments relate to drives that use methods and assemblies that incorporate electrical device components and continuously or infinitely variable transmission components.
Description of the Related Art
To provide a continuously variable transmission (CVT) or an infinitely variable transmission (IVT), various traction roller transmissions in which power flows through traction rollers between torque input and output rings have been developed. In such transmissions, the traction rollers mount on structures that when pivoted cause the traction rollers to engage the torque rings in circles of varying diameters depending on a desired transmission ratio.
A known CVT includes a shaft about which input and output rings rotate. The input and output rings mount on the shaft and contact a plurality of traction rollers disposed equidistantly and angularly about the shaft. The traction rollers are in frictional or tractional contact with both rings and transmit power from the input ring to the output ring. An idler located concentrically over the shaft and between the balls applies a force to keep the traction rollers in contact with the input ring and output ring.
An electric motor producing variable speed and constant power is highly desired in some vehicle and industrial uses. In such constant power applications, torque and speed vary inversely. For example, torque increases as speed decreases or torque decreases as speed increases. Some electric motors can provide constant power above their rated power; for example, a 1750 rpm AC motor can provide constant power when speed increases above 1750 rpm because torque can be designed to decrease proportionally with the speed increase. However, a motor by itself cannot produce constant power when operating at a speed below its rated power. Frequently torque remains constant or even decreases as the motor speed decreases. Controllers can be used to increase current, and torque, into the electric motor at low speeds, but an increase in the wire diameter of the windings is required to accommodate the additional current to avoid overheating. This is undesirable because the motor becomes larger and more expensive than necessary for typical operating conditions. The electronic controller also increases expense and complexity. Another method to achieve sufficient low speed torque is to use a bigger motor. However, this increases cost, size, weight, and makes the motor more difficult to package with the machine it powers. Thus, there exists a need for an improved method to provide variable speed and constant power with an electric motor. The continuously variable transmission can be integrated with an electric motor for some applications.